This application claims priority from Korean Patent Application No. 2003-7871, filed on Feb. 7, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to an apparatus used in semiconductor device fabrication, and more particularly, to a photoresist supply apparatus for a photolithography process used in semiconductor device fabrication.
2. Description of the Related Art
Generally, semiconductor device fabrication is a multi-step sequence from wafer preparation to semiconductor chip packaging. In detail, semiconductor device fabrication includes process steps such as forming thin films on a wafer, ion implantation for injecting dopants into the wafer, photolithographic processes for patterning the thin films on the wafer, testing semiconductor devices on the wafer, and cutting (dicing) the wafer into individual chips and then packaging of diced chips. Among the above process steps, in the photolithographic process, photoresists are used for pattern formation. The photoresist is applied as a thin film on the wafer and is subsequently exposed through mask to light to create a photoresist pattern.
FIG. 1 is a schematic illustration of a conventional photoresist supply apparatus and a photoresist supply scheme using the apparatus.
Referring to FIG. 1, a conventional photoresist supply apparatus 101 includes a first photoresist bottle 10 and a second photoresist bottle 30. A first photoresist 50 contained in the first photoresist bottle 10 is supplied into a photoresist pump 110 via a first photoresist supply line 60, a first trap tank 70, and a valve 90, and then dispensed onto a wafer. A second photoresist 130 contained in the second photoresist bottle 30 is supplied into the photoresist pump 110 via a second photoresist supply line 140, a second trap tank 150, and the valve 90, and then dispensed onto the wafer.
A photoresist supply scheme using the above conventional photoresist supply apparatus will now be described in detail with reference to FIG. 1.
When the first photoresist 50 is mostly consumed, i.e., the first photoresist bottle 10 is almost empty, during supply of the first photoresist 50, a first photoresist sensor 160, which is installed near the first trap tank 70, detects the absence of the first photoresist 50 and then transmits an electrical signal to the valve 90, thereby connecting the valve 90 to the second photoresist supply line 140. At this time, a first ON/OFF valve 190 of a first drain line 170 connected to the first trap tank 70 is closed. Therefore, supply of the first photoresist 50 through the first photoresist supply line 60 is stopped. It is understood that the first photoresist bottle 10 is changed to a new one for successive semiconductor device fabrication.
When the first photoresist 50 in the first photoresist bottle 10 is consumed, a photoresist supply is carried out using the second photoresist bottle 30 as explained below. First, nitrogen is supplied into the second photoresist bottle 30 via a nitrogen supply line 210. When the supplied nitrogen pressurizes the second photoresist 130 in the second photoresist bottle 30, the second photoresist supply line 140 and the second trap tank 150 are filled with the second photoresist 130 and residual air is released via a second drain line 230. When the supply of the second photoresist 130 containing no air into the second trap tank 150 is completed, a second ON/OFF valve 250 is closed. Accordingly, nitrogen supply through the nitrogen supply line 210 is stopped. The second photoresist 130 filled in the second trap tank 150 is supplied into the photoresist pump 110 via the second photoresist supply line 140 and the valve 90.
On the other hand, at an initial stage of the supply of the second photoresist 130 into the second photoresist supply line 140, air is present in the second photoresist supply line 140. If the air is incorporated into the second photoresist 130 while the second photoresist 130 passes through the second photoresist supply line 140, air bubbles can be generated, thereby adversely affecting a photolithographic process. Therefore, the air in the second photoresist supply line 140 must be released via the second drain line 230 and the second ON/OFF valve 250. That is, at an initial stage of the supply of the second photoresist 130 into the second photoresist supply line 140, the second ON/OFF valve 250 is opened so that the supply of the second photoresist 130 is carried out, simultaneously with releasing air.
In this way, when the second photoresist 130 is supplied through the second photoresist supply line 140 while the second ON/OFF valve 250 is kept open, a large amount of the second photoresist 130 is dissipated through the second drain line 230. That is, when a used photoresist bottle is changed to a new one, a large amount of a photoresist is wasted through the drain line 230. In FIG. 1, a reference numeral 270 denotes a second photoresist sensor detecting the second photoresist in the second trap tank 150. Arrows represented in the first photoresist supply line 60 and the second photoresist supply line 140 denote the flow of the first photoresist 50 and the second photoresist 130. Arrows represented in the second photoresist bottle 30 denote nitrogen flow directions.